1. Field of the Invention
The present invention relates to a filter for air extraction apparatus, air extraction apparatus and a method of manufacturing a filter for air extraction apparatus.
2. Description of the Related Art
Extraction systems for extracting and filtering air to remove air-entrained particulate matter and gases are known. Apparatus of this type is used in a wide variety of industrial situations such as, for example, in the electronics industry and in the pharmaceutical industry. Workstations on an assembly at which fume and/or dust generating operations are carried such as for example, the fabrication of electronic circuit boards, requires an extraction system. Fume extraction assemblies manufactured and sold by the present applicant under the trademark xe2x80x9cPurexxe2x80x9d include a number of articulating arm assemblies for different workstations, linked together by appropriate pipework to a pump and filter assembly.
Many filtering assemblies are known and it is also well recognised that a filter must be appropriate for the type of material that is being filtered from the air stream, the filter must provide the requisite degree of filtering and furthermore the filter must provide an operational period of sufficient length. Problems arise with many filtering systems of this type in that in order to provide an appropriate degree of filtering, it is possible that the life of the filter will be reduced. Similarly, if attempts are made to increase the operational lifetime of the filter it is likely that, at some stage, this will reduce the filtering efficiency.
According to a first aspect of the present invention there is provided a filter for air extraction apparatus assembled from a porous material arranged to collect contaminants, comprising a bag with a constricted inlet for receiving contaminated air, wherein said bag is formed from a plurality of envelopes having filtering side walls and each said envelope has at least one orifice connected to an orifice of an adjacent envelope.
Thus, since the filter comprises a plurality of connected envelopes, it provides an increased surface filtering area when compared to filter-bags having a single compartment.
According to a second aspect of the present invention there is provided an air extraction apparatus including a filter comprising a bag with a constricted inlet for receiving contaminated air, wherein said bag is formed from a plurality of envelopes, each of said envelopes has filtering side walls, and each of said envelopes has at least one orifice connected to an orifice of an adjacent envelope.
According to a third aspect of the present invention there is provided a method of manufacturing a filter for air extraction apparatus comprising a bag with a restricted inlet for receiving contaminated air, wherein said method comprises the steps of: providing a plurality of sheets of a porous material arranged to collect contaminants; defining an orifice in selected ones of said sheets; connecting said sheets to form a plurality of envelopes having filtering side walls such that each said envelope has at least one orifice connected to an orifice of an adjacent envelope.